One of the most common builder errors that home inspectors have to deal with is the installation of concrete surfaces over the top of wood siding—or any kind of siding for that matter.
It is not a good idea.
That bears repeating: IT IS NOT A GOOD IDEA.
Since so many builders install concrete in this manner, there is a perception, in the real estate community, that it must be OK. It is assumed that, at best, home inspectors are tilting at windmills for even bringing it up.
When I see concrete poured over siding, the information goes in the report. I know that 99% of the time nothing is going to be done about it. In well protected areas it might not even represent that big of a deal and of course some climates are more forgiving than others. I must offer a caution however, that given the right amount of wind driven rain, sprinkler systems or wet soils under the concrete work, problems can arise over time.
All parties want to hide their heads in the sand over the issue because of how difficult it is to make satisfactory repairs.
Take a look at the following picture.
Can you see that this concrete stoop covers three rows of siding and that the fourth row sits right on top of the concrete? While it may not be obvious to anyone that has not framed houses, you should be able to tell by where the door sill is that the stoop also covers the rim joist of the floor system. This means that we have not only the siding behind the concrete but the house sheathing and floor system are also behind the concrete.
What you are looking at is a totally typical installation that I see on just about every other inspection.
So what is the solution?
Well of course the best solution is to remove all the concrete and start over. All the wood materials that are going to be behind the concrete should be pressure treated lumber and properly flashed behind the concrete with metal flashings that will last “forever.” These metal flashings should be over a foundation grade rubber membrane. There should be proper clearances to wood siding all around the concrete work leaving the metal flashing visible. This would be considered “best practice.” We should think of these house components as being below grade—because in a very real sense they are.
So, since we know that this repair is not going to happen, what is the next best thing to “try” to do? I say “try” because anything short of “best practice” is never going to get warranted by a builder that knows what they are doing—at least one that is planning on being in the business for a long time.
One approach that I see sometimes is to caulk the connection with the wood and the concrete. We all know about the longevity of caulk—so this is not the best long term solution. Another thing that caulking does, besides preventing water from flooding behind the concrete work, is that it prevents moisture from the ground from having a way out from behind the concrete, thus promoting elevated moisture in the wood behind the concrete. Caulking the connection may not accomplish the desired result and may actually make matters worse.
Another approach that I like better is to remove as much of the siding as possible and insert appropriate flashings that extend out over the concrete work. A vapor permeable weather-stripping could be installed between the concrete and the flashing. This will keep most surface water out and prevent moisture from being trapped behind the concrete—somewhat.
Of course doorways that are flush with the concrete are not likely going to get addressed in this scenario and no one is likely going to remove the doors to properly flash them as is necessary.
Again, as we have discussed, this solution is not ideal, but in light of no one being willing to make proper repairs it may be the “solution” we are stuck with.
Just in case you are wondering just how much damage can “really” happen, or whether I am truly merely tilting at windmills, here are a couple of pictures of the actual damage that has been partially uncovered in the area behind the stoop pictured above.
There was evidence of Moisture Ants, Carpenter Ants, Dampwood Termites and Wood Decay/Rot all involved in this damage. At the exterior of the home—right where one of the siding boards disappears behind the concrete stoop there is a Carpenter Ant “window” visible if you know where to look. They make these windows for kicking out frass and for coming and going. Sometimes I think they might actually BE windows—but I am not an ant.
The white color in the next picture is the concrete stoop itself that is visible where the rim joist and sheathing have been completely destroyed.
So while I may be tilting at windmills the wind is blowing in my favor.
By Charles Buell, Real Estate Inspections in Seattle
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I found this post very helpful. We are getting ready to do a concrete stoop outside of our kitchen door and it has the exact same configuration as shown here in your post. Do you have a picture of the ideal configuration described in your post. How do we properly pull concrete away from the kitchen wall and leave a clearance?
I wish I did, but mostly pictures of it being done improperly. The illustration above basically describe it but instead of the flashing going out over the concrete it would run all the way down behind the concrete. Of course any wood the flashing covers should be pressure treated wood.
This is a wonderful post. We are planning a ground-level patio off of a new construction house and this helps us to know how to do it correctly. Our full basement has walk-out steps buttressed by two concrete walls. The siders installed James Hardie siding directly across the tops of these walls resulting in a combined length of about a foot where we do not have the required inch between the siding and the concrete. What would you suggest? Thanks so much for sharing your expertise!
Hard to visualize Linda, but your flat-work installers should know how to handle the installation and still meet code requirements.
Is flashing needed for concrete steps to a concrete foundation? No wood. I just had a home inspection and this was noted to check with a professional as to the requirements. The steps have been there 20+ years without issue.
Susan, please post a picture
How do I install vinyl siding around my concrete stoop? Do I need starter strip or j channel between the concrete and my door?
Rachel, I recommend checking the vinyl siding installation instructions for this detail.
How do I fix a raised pit for patio that rotted out the sheathing?
Please attach some pictures
Having been a real estate agent previously, I know that one of the most common places for termite entry is between concrete front porch stoop and foundation. I have access to the rim joist from inside the basement and am wondering if an alternative to the unsightly drilling the porch would be to drill through the rim joist and pump in a non repellent termicide. I know that I may not form a complete barrier, but it seems like with the non repellent termicides that would be less important than in the old days. Are you aware of any professionals treatng homes this way?
This is the closest explanation of what I’m trying to fix right now. The porch was not installed over the siding, but the siding was trimmed a couple of inches beyond the porch, now I’m left with an ugly perimeter around the porch and don’t know how or who to call to fix it. I would love if I could send you a picture for advice. Is that possible? (Oh! I just noticed the attachment function below…)
These installations are so easy to get right at the time of construction and so difficult to fix after the fact. Sometimes with the siding, trim and door out of the way, a flashing can be slid in between the house and the concrete. Other times an L flashing over the surface of the concrete and work but keep in mind this can also trap moisture behind the the concrete. Large roof overhangs can provide protection in some cases. Sometimes the concrete can even be moved enough to make a gap for flashing. That is all I got for you. Good luck with it.
Thank you for your response. I may look into having an overhang installed and investigate flashing and finishing ideas,
This is the closest explanation of what I’m trying to fix right now. The porch was not installed over the siding, but the siding was trimmed a couple of inches beyond the porch, now I’m left with an ugly perimeter around the porch and don’t know how or who to call to fix it. I would love if I could send you a picture for advice. Is that possible? (Oh! I just noticed the attachment function below…)
Hello Charles,
I have a home built on a stem wall with hardieplank siding. We had a contractor build a deck off the back of the house. The deck was attached to the plate that runs along the top of the stem wall faceplate. The issue is that he did not put any flashing or any material
between the pressure treated 2z12 and the siding. It actually looks like the chemicals in the wood are eating away the siding. Have you seen this in for inspections? It’s a large deck, nailed and bolted to the house and will be a lot of work to undo everything. I was thinking of pouring some type of material between the wood and the siding as there is a quarter inch gap at the top where the wood and siding don’t touch, I assume because of the angle of the siding. would this be a waste of time and money and if you do think it might work what would you suggest?
There is no prescriptive way to allow or correct installation of a ledger over the top of siding. An engineer might be able to design a repair that would allow the siding to remain as long as the top of the ledger was flashed behind the siding properly.
Hi, I am in Denver Colorado. I am have made A lot of effort to pour a raised concrete patio at my parents house. I really want to do the right thing and give them a lasting patio that does not mess with the framing of the house. I have already poured a retaining wall all the way around the house. I have also poured a retaining wall up to the house. The finished, product would cover 12 inches of the house, the first floor framing by 14ft.. I can still install flashing and other waterproofing but if I just need to knock down the retaining wall and start over the I will have to do that. It will be a ton of work. I just need to know if I need to rip it up and start a new patio at ground level or if I can actually pour concrete with the flashing and or other waterproofing correctly to accomplish this. Can you help me make that decision.
I cannot tell enough from what you have written to tell what you have going there. Pictures would help.
Hi Charles,
We’re in Indiana. We’re pouring a new patio with two steps going into the house. I know we need to cut the vinyl siding away from where the stairs will meet the house, but how do I install the flashing, how far down & side to side, what should the gap be between the new concrete & the vinyl, should I use house wrap paper between the flashing & the house….? Several questions….
I wish I had an easy answer for you because what you are attempting creates a couple of problems. In my opinion some sort of impervious membrane should be installed over the sheathing and behind the flashing—both of which should be lapped by the siding and the flashing should have 2-4 inches exposed between the concrete and the siding. It would be best practice to replace the sheathing in the area to be covered with pressure treated plywood of the same thickness as the current sheathing. I consider it best practice to use copper flashing as sooner or later the coated steel flashing will rust/corrode depending on how much salt you use on the surfaces. No aluminum flashings. I must stress, this is “general advice” and may not cover all the scenarios present. Consult with a builder experienced in these installations.
Thanks Charles, that just reassures us that what we’ve decided to do is correct. We’re covering the OSB w/ house wrap material & then using galvanized steel over that. The only question I have now is whether caulking around the flashing is necessary, & if so, what kind. If I didn’t get any advice on that issue, I was just going to go ahead & seal it up w/ an all-weather silicone….
I think 50 year Butyl caulks are better than silicone
Hi,
Im having concrete steps poured against the house, under patio doors. Approx 3 ft in height. Im installing pressure treated plywood, then house wrap around plywood and metal lath. Is this enough to protect the plywood from rot? Should there be a gap between house and concrete steps to allow air flow? If so, 1/2 inch or more?
House wrap and a good drainage plane material would be a good idea.
This blog is very informative, I recently purchased my first house which has similar problem.
1. there is concrete touching the siding/band board(? am I right), there is gap and water entering when heavy rain
2. you can notice the gutter pipe going down, at that point roof ends, allowing water to fall on this area of concrete
3. the band board has rot, luckily there is no rot in the inside of crawl space adjacent
I need your guidance on how I can address…
1. is the band board replaceable to fix rot? what I should expect?
2. what is the ‘better’ way to fix the gap?
3. Can I also extend the roof until the concrete and wall meets, to reduce water?
This horizontal trim board is not structural, however it likely covers structural components like the band joist and sill plates etc. Depending on how the sheathing and house wrap were done this can still, over time, allow damage to occur. The amount of damage that can occur, or can be anticipated to occur, can also be affected by how exposed to the weather it is, or protected by overhangs. I typically recommend repairs when damage occurs due to the difficulty of making repairs. Sealing the gap can exacerbate the problem as it will not let water out, even while it allows water in. A conundrum for sure. Ultimately, removal of the concrete and proper treatment, installation, protection of the house structure is necessary prior to reinstalling the concrete may be necessary. I think at the time of construction, if enough builders were called to the carpet for this installation, things might change.
Thanks a lot Charles. I understand that you are in Seattle area and I am in Eastside. if you know of anyone who could do such repair feel free to refer and share contact.
thanks again!!!
Additional picture for the last scenario. Many thanks for your guidance.
Inside view picture for last scenario.
I’m dealing with exactly this situation and I’ll admit I over did it on the fix. The skirt board (pine), sheathing (OSB), and band joist (OSB) were all untreated and below/behind the concrete stoop. Removed flagstones, cut concrete down well below the sill plate and about 5″ out. Demo’d everything, put in 2″x12″ PT band joist, adhesive flashing (protecto wrap), painted aluminum flashing, and then blueskin (mostly because I had a 12’x3′ piece around). Filled the concrete gap and made a copper door sill pan and ‘L’ flashing back to the concrete level. Putting the flagstone back now and will add a final piece of copper ‘L’ flashing below the door sill trim piece (Western Red Cedar primed/painted on six sides) and will leave about an 1″ of clearance between the trim/siding (also WRC) and the top of the flagstone. This is in a house that is 10 years old.
Dealing with this now on my front stoop. I probably over-flashed it during the rebuild, but I think it’s better than it was and should last longer than me at least. I attached a couple pictures during the deepest part of the demo.. removed flagstone, cut concrete back and below the foundation and had to take out ~13′ of band joist (OSB) and patch parts of the sill plate with 2x PT and ‘above grade’ areas of sheathing were replaced with sheathing and tape as needed. Put a 2×12 PT band joist back in, flashed with adhesive butyl wrap up to the door sill and down onto onto the foundation, flashed over that with painted aluminum cut into the sheathing at the bottom of the door, flashed over that with blueskin (mostly because I had some around), built a copper door sill pan, brought the concrete back up to original level and again flashed from the door sill pan down to the concrete with ‘L’ shaped copper flashing. Putting the flagstones and siding back on now.
FYI- that top image needs to be rotated 90 degrees clockwise. Those are the ends of the floor joists you see in the bottom image and that’s the trough I excavated from the concrete stoop.
I’m in Tennessee and just got new siding on my house today, I’m not sure if the bottom part will keep water out. It does have house wrap behind it, but I’m eye balling the lip where it meets the concrete as a way for water to leak in. Is this OK, or does it need to be sealed somehow?
I can’t tell from the picture what is covered up. It may be fine it may not. Caulk should never be a “primary” means of water penetration protection. I can tell you they have not left enough of a gap between the flashing and the siding.
Flashing for siding is only made to shed bulk water.
I saw this kind of flashing on a hospital parking lot
and I would like to use it on a job that I am planning
but I have not been able to find it or any information
on it.
I don’t know what you mean when you say
they have not left enough of a gap between the flashing and the siding.
I went there on a rainy day and it looked like it worked like I would
like it to work, the rain that would normally get into the crack between the wall and
driveway would hit the flashing and go into the driveway.
This system was second one used , the first was a 3×3 x1/4 inch vinyl angle
glued to the wall that did the same with the rainwater.
I could not find the angle vinyl either
I believe he was saying that, because the bottom edge of the bottom siding board is touching the metal flashing. It appears to be concrete composite siding like Hardie plank. If so, the edge that comes in contact with the flashing can absorb water into and behind the siding.
Usually, you would have a gap at that location of 1/4 inch to 1″ depending on the siding type.
(I know this is an old thread, but in case someone else is reading)
We purchased an old 1910 house a couple of years ago and the concrete porch was poured up against the house, slightly above the bottom piece of siding. The porch wraps around 1 side and part of the back, where it is on the back the porch is not covered. We are now replacing floor joists and wall studs from where the porch was poured and not properly flashed. It was not even mentioned in the home inspection. Sometimes we learn things the hard way
I appreciate your article. We just purchased a home with hardie plank that has 1/2 in crack in siding where patio has settled. It does catch rain that hits house at an angle and wonder if we should remove or cut back patio to see if there is damage or should fill gap and install flashing over it.
Inspection of crawl space didn’t see damage under house. It does have house wrap under siding.